1. Field of the Invention
The invention relates generally to biopsy needle guidance by employing an x-ray/gamma image spatial co-registration methodology. Further, the invention relates to using a plurality of gamma camera images taken at different positions to identify breast lesion location. Moreover, the invention also generally relates to a breast lesion localization method using opposed gamma camera images or dual opposed images.
2. Related Art
X-ray imaging of the breast provides high spatial resolution images of changes in breast tissue density. These density changes may be due to a number of factors such as age, pre- and post-menopausal tissue changes and the presence of various pathological conditions. X-ray imaging is a commonly used technique for breast cancer screening and diagnosis, but since it also is sensitive to other non-malignant pathologies, its accuracy is compromised. The specificity of x-ray imaging may be quite poor with only about 20% to about 35% of biopsies yielding cancer diagnoses. It is also a commonly used modality for breast tumor needle biopsy guidance, but has been found to be lacking in target accuracy for some cases.
Nuclear medicine breast imaging techniques may yield accurate physiological data, but with a lower spatial resolution than that obtained with x-ray imaging. This physiological imaging is much more specific than x-ray imaging, with about 70% of positive studies yielding a cancer diagnosis. Also, since it detects physiological abnormalities, it directly indicates the location of disease, while x-ray imaging is limited to detecting changes in tissue density which may be secondary to the presence of disease.
Another important area of diagnostic concern is the accuracy of a stereotactic needle biopsy. This biopsy procedure has been proven to be effective in managing most patients demonstrating suspicious mammographic findings in screening mammograms. Due to its less invasive nature, this procedure may be more desirable to perform than other biopsy procedures. Despite the promising role of this procedure in breast lesion management, however, some clinical studies have found a false negative rate of about 10%. Moreover, findings from additional studies point toward specific subgroups limiting the diagnostic accuracy of this procedure. The first of these subgroups consists of cases in which the needle biopsy underestimated the extent or type of disease. In these studies, needle biopsies indicating atypical ductal hyperplasia or ductal carcinoma in-situ were often upgraded to infiltrating ductal carcinoma upon open biopsy or follow-up. In addition, another study found that the diagnostic accuracy of needle biopsy was dependent on lesion size, as masses larger than about 3 cm were less likely to be diagnosed correctly.
Scintimammography is a functional, biomolecular breast imaging procedure that is typically conducted with large field-of-view gamma cameras. The efficacy of this procedure is lacking for diagnostic accuracy for lesions less than about 1 cm in diameter, non-palpable masses, and lesions located in the medial aspect of the breast. Several investigators have hypothesized that these limitations may be due to the use of non-optimized large field-of-view detectors and suggested the study accuracy could be improved with dedicated small field-of-view systems. Such systems may allow the breast to be compressed against the collimator to optimize image spatial resolution. In addition, these detectors may be positioned to allow the breast to be imaged from several angles including the medial views. Improved spatial resolution may lead to improved lesion visibility and therefore higher sensitivity. Accordingly, there is a need to improve the exiting imaging methodologies and techniques.